The present invention relates to electronic circuits, and in particular, to an electronic circuit that deciphers between AC and DC input signals.
Electronic devices typically use power from alternating current (“AC”) and/or direct current (“DC”) sources. For example, an electronic device may receive an AC power signal from an AC power source for its power, or may receive an AC power signal from an AC power source for internally deriving a DC power signal for its power, or may receive a DC power signal from a DC power source for its power. Some electronic devices could use both AC power signals and DC power signals concurrently for its power. In many industrial applications, AC power signals may be provided by AC power sources between 87 to 265 Volts at 50 to 60 Hertz, and DC power signals may be provided by DC power sources between 18 to 32 Volts.
Industrial controllers, such as programmable logic controllers (“PLC's”), are specialized electronic computer systems used for the control of industrial processes or machinery, such as in a factory environment. Industrial controllers differ from conventional computers in a number of ways. Physically, they are constructed to be substantially more robust against shock and damage and to better resist external contaminants and extreme environmental conditions. The processors and operating systems are optimized for real-time control and execute languages allowing ready customization of programs to comport with a variety of different controller applications. Industrial controllers may also have a user interface for accessing, controlling and/or monitoring the industrial controller, such as through a locally connected terminal having a keyboard, mouse and display.
Industrial controllers often have a modular architecture that allows different numbers and types of network cards or adapters to be used to connect the controllers to electronic devices or field devices, such as sensors and actuators for controlling and interacting with industrial processes and/or machines. Field devices may be dedicated to a particular function, such as detecting an input signals or running a motor, and may be located at convenient control points near the industrial processes and/or machines. Field devices may receive AC and/or DC power locally, or in preferred applications, may receive AC and/or DC power from the industrial controller.
Electronic devices or field devices require correct power in order to operate correctly. Receiving an incorrect power signal could potentially result in immediate and/or long term harm to the electronic device and/or catastrophic conditions, including possible fire, personal injury or death.